Do Venous and Arterial Base Excess Agree in Trauma Resuscitation? Experience of a Military-Relevant Severe Injury Swine Model

INTRODUCTION: Arterial and venous base excess (BE) measurements are correlated in stable conditions. However, controversy exists whether there is concordance between them in shock and resuscitation, especially when aortic occlusion (AO) is required. We used our novel, military-relevant dismounted complex blast injury swine model to test the hypothesis that venous and arterial BE are not concordant in severe injury and resuscitation. METHODS: Eight swine underwent dismounted complex blast injury (blast brain injury, femur fractures, hemorrhagic shock) followed by aortic occlusion with resuscitative endovascular balloon occlusion of the aorta (REBOA), albumin, and shed blood transfusions. Deep shock was achieved while maintaining constant pCO2. Agreement between simultaneous arterial and venous BE was assessed using the intraclass correlation coefficient and Bland-Altman plots. Linear mixed models accounted for repeated measures by animal. RESULTS: There were 51 arterial/venous BE pairs across 4 experiment phases (Initial instrumentation, Shock, REBOA, and Resuscitation). Mean arterial-venous BE difference (AVD) was 1.9 mEq/L (SD 5.0, interquartile range 0 to 3.0); 54% had an absolute AVD greater than 2.0 mEq/L. Arterial and venous BE had a quadratic linear relationship (quadratic term p = 0.0004), not affected by acidosis (interactions p > 0.13). Although the the overall intraclass correlation coefficient was 0.79 (95% CI 0.66 to 0.87), suggesting good agreement, it varied widely by experiment phases: initial instrumentation, 0.32 (95% CI –0.41 to 0.80); shock, 0.35 (95% CI –0.60 to 0.89); REBOA, 0.04 (95% CI –0.49 to 0.55); resuscitation, 0.89 (95% CI 0.78 to 0.94). The Bland-Altman plot (Figure) showed that, overall, 84.3% of AVDs were less than 1 SD; however, only 64.7% were within the interquartile range. The AVD proportions inside the interquartile range by experiment phase were as follows: initial instrumentation, 87.5%; shock, 75%; REBOA, 41.7%; and resuscitation, 78.6%.Figure.: BE, base excess; REBOA, resuscitative endovascular balloon occlusion of the aorta.CONCLUSION: Although venous and arterial BE correlate, they often show substantial discordance, especially during shock and aortic occlusion. Thus, venous and arterial BE should not be used interchangeably to monitor severely injured patients’ response to resuscitation.